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Status and Prospects of SPS Magnet Consolidation Program
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  1. Status and Prospects of SPS Magnet Consolidation Program SPS Beam Lines In the Way to the LHC

  2. Outline Introduction Auxiliary magnets and equipment • Magnets • Equipment Main magnets • Erosion • Fatigue • Statistics 2008 – 2009 Prospects for 2009… 2010 Impact of non shutdown 2009 – 2010 Conclusion

  3. Outline Introduction Auxiliary magnets and equipment • Magnets • Equipment Main magnets • Erosion • Fatigue • Statistics 2008 – 2009 Prospects for 2009… 2010 Impact of non shutdown 2009 – 2010 Conclusion

  4. Introduction - Magnets in the Way to the LHC • January 2008: ‘MTTR and Spare Policy for SPS Magnets’ has been adressed by D. Smekens to ATC-ABOC days Main magnets, continuousrefurbishment program New magnets in injection lines TI2/8, sparesavailable Criticalsince large familieswith few spares, but magnets are quitereliable Large families Courtesy of D. Smekens

  5. Introduction • Reminder of the conclusions: • No specific risks for auxiliary magnets: generally small families of magnets with spares available for most of them • Main magnets are top priority since they constitute the largest families with few spares, and have a high risk of breakdown due to important solicitations (operated at saturation, high water flow speeds, no valves…) • need close monitoring of performance and early detection of possible accumulation of breakdowns that could be forerunner of illness (e.g. water leaks  erosion) • Main scope of this presentation will be the main magnets

  6. Outline Introduction Auxiliary magnets and equipment • Magnets • Equipment Main magnets • Erosion • Fatigue • Statistics 2008 – 2009 Prospects for 2009… 2010 Impact of non shutdown 2009 – 2010 Conclusion

  7. Auxiliary Magnets • Several issues in auxiliary magnets could perturb the operation of the LHC: • Few spares are available for several magnet families most of which are mandatory for the LHC operation (MPLV, MPSV, LS/LSN, LO/LON, B340…) • Large majority of the spare magnets are not tested  could increase MTTR if there is a magnet failure • Use of spare magnets for new projects (e.g.HiRadMat) could lead to a significant decrease of available spares for some families (MDSV, MBS) • Many of transfer line quadrupoles (QTL, QTA, QNL) have degraded shimming that can generate coil movements  low reliability (water leaks, short-circuits to ground), but many spares are available from WEA • However, inspections led on the auxiliary magnets at the beginning of this shutdown have shown no major reliability issue • Our goal is now to have at least 1 operational spare (tested) for each magnet type ASAP

  8. Auxiliary Equipments • Breakdowns of ancillary equipment that could also impact on accelerator operation: • Degradation of water hoses in use for more than 12 years  need to be replaced (≈10 Km of hoses, ≈5000 fittings)  to be done (TE/MSC) • Flashover between busbars  need inspection and cleaning  To be completed at the same time as water hoses replacement (TE/MSC) • Failure of water cooled cables (no spares installed, no spares available at the moment)  investigations of risks of erosion inside cooling ducts inside cables  in progress (collaboration TE/MSC – EN/EL) • Reliability issues of installation vehicles used for main magnets  need complete refurbishment and upgrade for future projects  in progress by EN/HE • Risk score to suffer such an event can be kept very low if appropriate actions are undertaken / pursued

  9. Outline Introduction Auxiliary magnets and equipment • Magnets • Equipment Main magnets • Erosion • Fatigue • Statistics 2008 – 2009 Prospects for 2009… 2010 Impact of non shutdown 2009 – 2010 Conclusion

  10. Main Magnets – Erosion Issues Usual issues are linked to ageing which is translated in erosion and fatigue phenomenon's • Erosion In places where high flow speed crosses sharp transitions  effect is critical in thin copper tubes: water leaks • In dipoles: • Lintott coils (2/3 of MBB’s): due to design of the coil, flow reaches 9 m/s in some places. Consolidation program achieved over the 3 last shutdowns to replace all manifolds by improved design:  255 magnets in the machine equipped with these coils + all spares (even with Alsthom coils) have been refurbished Original design New design

  11. Main Magnets – Erosion Issues • Alsthom coils (1/3 of MBB’s + all MBA’s): erosion induced water leaks also occur in these coils, but at a much lower rate than in Lintott coils. Also, leaks are generally located in non conform manifolds in which the section has been thinned or deformed by a bump (generation of higher flow speed and turbulences) or in which the wall thickness has been decreased by grinding  Inspection during this shutdown has shown non conform manifolds on 24 magnets: deformed parts of tubes have been replaced to lower the risk of leaks. However, a consolidation (upgrade) like Lintott’s should be necessary sooner or later Bumps Grinded tube Tube partiallyreplaced

  12. Main Magnets – Erosion Issues • In quadrupoles: 1 erosion induced water leak occurred at the end of run 2008. •  Phenomenon is currently being studied. Recent endoscopies have already shown it is not a generalized problem,but quiteextended. Following results, a consolidation could be necessary soon (next shutdown ?). A solution consisting in the replacement of all thin tubes could be implemented in 1 shutdown in situ. Water leak Erosion craters

  13. Main Magnets – Fatigue Issues • Fatigue Due to tens of million of pulses accumulated over 35 years of operation (although SPS initially designed for 50,000 h !)  effect translates in different manners among the magnet families: • In dipoles: • Break of the fastening screws of the magnetic correction pole shim : phenomenon discovered this shutdown during inspection under magnet patrol access mode (main magnets pulsed). Currently being studied with help of EN/MME/MM 2 pole shim sets ateach end of dipoles

  14. Main Magnets – Fatigue Issues • Pole shim system designed to adjust the magnetic length to match it with a reference magnet by adding lamination on pole ends (reproducibility of integrated field) M8 cylindrical head screws, steel class 12.9 1 to 10 laminations added (th.1.5mm) Spring pins

  15. Main Magnets – Fatigue Issues In total, 26 pole shims were found defective on 18 magnets (16 MBB’s and 2 MBA’s) Possible causes:  non conform mounting (unadapted screw length or tightening torque)  high number of occurences could be due to accumulation over last 2 or 3 years (not detected during previous inspections ?)  to be checked with results of future inspections sollicitations of run 2008 were more intense, with return of pulses at 450 GeV/C. Indeed, previous occurrences were already encountered during operation at 450 GeV/c between 1980 and 2000. Brokenhead of screwtrimminginto the vacuum chamber and the coilinsulationateach pulse Head of fasteningscrew and spring pin broken Pole shimmovingawayfromits position Magnetic correction laminationsfallingapart

  16. Main Magnets – Fatigue Issues Consequences:  degradation of the magneticfieldquality of the magnetsduringoperation (someshimswerefound on the ground)  degradation of the coilinsulationleading to short-circuits to ground (1 case foundduring HV test): the end shimdisplaceddiagonallytrimsinto the insulation of the coil Strategy to consolidate: • 1st step: repairing of the broken pole shims found this shutdown before the SPS restart in march • Only 40% could be repaired in a corresponding way (i.e. with new screws and pins) • For the 60% remaining, impossible to remove both screws in situ  laminations and end shim had to be glued. In addition, dismountable external fastening devices are being manufactured to allow keeping the pole shims in place up to next shutdown ( consolidation) • 2nd step: analysis of the phenomenon to define if upgrade of the system is needed • Analysis of broken screws collected (EN/MME/MM)  in progress • Computations of a model + tests in laboratory  to be done during run 2009

  17. Main Magnets – Fatigue Issues • 3rd step: implementation in situ of solution based on results of study • If no or small upgrade is required, replacement of the screws (≈6000 units) with appropriate mounting by screws of same size (other steel quality could be chosen) • If upgrade is required, need to develop adapted tools to allow modifications (M8  M10) in situ (few space available)  In both cases, has to be done (or at least started) during next shutdown MBB isometricview – connectionside

  18. Main Magnets – Fatigue Issues • Longitudinal displacement of coil inside the yoke: phenomenon discovered on 5 dipoles (3 MBA’s, 2 MBB’s) during this shutdown inspection. Coils are shifted up to 40 mm towards connection side, in some cases pushing the vacuum chamber of the dipole upstream. • Possible causes: accumulation of movements over the years (neverdetectedbeforebecause amplitude of movementwastoosmall?) ; degradation of soft shimming ; kapton foil wrappedbetweencoil and yokedecrease friction coefficient ; pulses at 450 GeV/C ? •  Disassembly of the magnets (run 2009) willproduce more information Coilshifted of 30 mm w.r.t. nominal position Vacuum chambertrimminginto the coilinsulation

  19. Main Magnets – Fatigue Issues • Consequences: degradation of the magneticfieldquality of the magnetsduringoperation (corrections done by BE/OP last runseem to coroboratethisfact), degradation of the coilinsulationleading to short-circuits to ground • Actions: • - All magnetswiththisproblem have been replaced • - Measurementcampaign of longitudinal position of all coilsisbeingcompleted • - Adaptedcoilretainerscouldbedesignedduringnextrun and put in placeduringnextshutdown (e.g.Vetronite blocs put down on the magnetfeet) Coilretainerinstalled in the machine (Vetronit plate and blocks)

  20. Main Magnets – Fatigue Issues • In quadrupoles (QD/QF) and enlarged quadrupoles (QFA/QDA): • Coil movements: due to degradation of soft shimming between coil and yoke (radiation, temperature, hardening). Result in fatigue of the copper tubes and brazed junctions of the manifolds  water leaks • Corrective action for QD/QF: preventive exchanges (average of 3 / shutdown) and continuous refurbishment activity in adapted facility in radioactive workshop b.867 • Corrective action for QDA/QFA: shimming in situ with Vetronite pieces glued with Araldite since no reconstruction facility / procedure are available at the moment. 3 spare magnets are available (1 fully operational) for 14 magnets operated SPS Main quadrupole SPS Main enlargedquadrupole

  21. Statistics Main Magnets 2008 - 2009 • Results: 5 interventions during run period, 15 magnet exchanges during shutdown period (3 for vacuum chamber coating project SPSU) Interventions run 2008 & magnet exchanges shutdown 2009 on main magnets Breakdown statisticsrun 2008 – shutdown 2009 on main magnets

  22. Outline Introduction Auxiliary magnets and equipment • Magnets • Equipment Main magnets • Erosion • Fatigue • Statistics 2008 - 2009 Prospects for 2009… 2010 Impact of non shutdown 2009 – 2010 Conclusion

  23. Prospects for 2009… 2010 • Refurbishment of all spare main magnets (taken out of the machine + in storage) during next shutdown, to be ready if we should encounter drastic reliability issues (pole shims on dipoles, waterleaks in quadrupoles…) • Prepare at least 1 spare magnet fully operational for each magnet type, starting by highest risk scores = f (impact on LHC and other facilities, ratio number of magnets in operation to number of spares, reliability) • Design and prepare implementation of pole shim consolidation + coil retainers • Prepare manifold consolidation ofquadrupoles • Prepare a global replacement campaign of the rubber water hoses in the whole SPS complex • If resources available, restart QTL/QTA refurbishment program

  24. Outline Introduction Auxiliary magnets and equipment • Magnets • Equipment Main magnets • Erosion • Fatigue • Statistics 2008 – 2009 Prospects for 2009… 2010 Impact of non shutdown 2009 – 2010 Conclusion

  25. Impact of non shutdown 2009-2010 • Program of magnet maintenance mainly based on results of general inspection performed in magnet patrol access mode at the beginning of the shutdown  gives a complete overview of the state of magnets, allows early detection of illnesses and leads to preventive and corrective actions on the magnets (exchanges, modifications, upgrades…) • Scenario with no shutdown seems unrealistic, moreover with an operation at 450GeV/c which makes more demands on the magnets  could decrease drastically the reliability of the machine without any signs (if no inspections) • Considering a scenario with a shortened shutdown (2 weeks of effective work), the following actions would be mandatory to ensure a quite reliable operation of the magnets in the SPS complex as LHC injector (i.e. except TDC2 and NEA): • High tension test on the main magnet system (magnets, busbars, water-cooled cables) in collaboration with TE/EPC + test of the imbalanced current detector: ½ day, machine closed ; • Inspection of the main magnets in the ring (access mode ‘magnet patrol’) + magnets in the transfer lines (mainly QTL’s in TT40 and TT60): 3 days (1 to open the covers, 1 for the inspection (machine closed), 1 to close the covers) • Exchange (not preventive, only corrective) or repairing of the defective magnets (pole shim screws broken, water leaks, short-circuits detected with the HV test…): approximately 1 day / magnet, following the type of defect ; • Therefore, main impact would be that neither preventive exchanges of magnets nor programs explained before (consolidation of pole shims, replacement of water hoses…) would be possible  risk to decrease reliability

  26. Outline Introduction Auxiliary magnets and equipment • Magnets • Equipment Main magnets • Erosion • Fatigue • Statistics 2008 – 2009 Prospects for 2009… 2010 Impact of non shutdown 2009 – 2010 Conclusion

  27. Conclusions • Recent findings confirm what we already know: the SPS main magnets suffer ageing issues, and need maintaining if one wants to operate this machine for some additional decades with the LHC • Careful monitoring of the magnet performance by frequent inspections is the only way to avoid suffering drastic reliability issues. With ~1000 units over 2200 in the way to the LHC, they are the keystones of the SPS link in the injector chain • Consolidation of pole shims and quadrupole manifold refurbishment have to be done soon to ensure reliable operation • We strongly recommend to have at least one short shutdown to perform careful inspections

  28. References • MTTR & Spare Policy for the LHC Injectors & Exp. Areas, David Smekens • Report to the PAF WG on the Status of the Magnets in the Existing Accelerators, W. Kalbreier, S. Ramberger, D. Smekens, T. Zickler, K. H. Mess • SPS Main Dipole Exchanges in 2007 & Next Shutdown Work, J. Bauche, W. Kalbreier, D. Smekens • New Strategy for the Repair of SPS Dipole Water Manifolds, J. Bauche, S. CettourCavé, W. Kalbreier, D. Smekens(EDMS Doc. No.: 783313)

  29. Annex 1: Overview of the Complex SPS as LHC Injector • SPS as LHC injectorincorporate: • TT10 Beam Transport Tunnel fromPS extraction (TT2) to SPS Injection point in Sextant 1 • SPS Main Ring • TT40/TI8 injection tunnel; • TT60/TI2 injection tunnel; • 13500 m of beam line • 2200 magneticelements on LHC way

  30. Annex 2: Fatigue Phenomenon - Wöhler Diagram